Improving the Effectiveness of Aerial Pesticide Sprays

Thirty-eight aircraft setups were submitted in order to have droplet size and drift analyses performed. Four of the eleven insecticides predicted Dv0.5s were in the 351–400 μm range. Seven of the herbicide setups had predicted Dv0.5s in the 205–250 μm range, while ten Dv0.5s were > 351 μm. Five of the ten predicted Dv0.5s were between 386 and 413 μm. Twelve different herbicides were reported as having been applied with aircraft setups that had predicted Dv0.5s between 386 and 413 μm. A summary of the prior swath deposit data indicated that the percent recovery generally increased as the Dv0.5 increased. The magnitudes of the deposits on inert targets and cotton leaves appeared to be about equal for a given Dv0.5. The correlation coefficient between the “percent of the spray volume in droplets ≤ 100 μm and ≤ 200 μm in diameter” was 0.983. This result is consistent with prior results and indicates that either 100 or 200 μm can be effectively used as the upper limit when studying the “small droplet” component in sprays. We found several similarities or differences in the “small droplet” components based on data from different atomization tests. According to one set of atomization models, agricultural aircraft will be limited to about 225 km/h (i.e., 140 mph) in order to produce a 400 μm Dv0.5 spray when using currently available nozzles and water plus one or more pesticides. The extremes of the predicted drift deposits for 38 agricultural aircraft setups were over 30-fold apart.